Update git submodules

* Update docs/submodules/fuel from branch 'master'
  - Rectify nova placement API check

    * make a GET request to placement service as it returns 200 with
      version data starting from nova 17.0
    * turn on nova image preallocation mode on baremetal computes
    * double salt worker threads by number of available CPU

    Change-Id: I509cbab3b4b8460452f5e487e457edfedd5da29a
    Signed-off-by: Michael Polenchuk <mpolenchuk@mirantis.com>

diff --git a/docs/submodules/fuel b/docs/submodules/fuel
index 06c464a..bc70493 160000 (submodule)
--- a/docs/submodules/fuel
+++ b/docs/submodules/fuel
@@ -1 +1 @@
-Subproject commit 06c464a9c2aee9cbfa801b2f3842bd0beca62291
+Subproject commit bc70493008a9194ec215214c97175d870eadcbf8